[VOTE][LAZY] Create GROOVY_5_0_X branch

Hi folks,

As we get close to the 5.0.0 release, I plan to create a GROOVY_5_0_X
branch as per our normal conventions and master will become 6.0.0-SNAPSHOT.

This vote will remain open for 72hrs and since it is lazy, I'll then
proceed unless there is further discussion to proceed on an
alternative path.

Cheers, Paul.